It comes down to something called polyphenol oxidase, explains Keri Gans, RDN, host of The Keri Report podcast. This is the enzyme that’s thought to make bananas turn brown when they’re ...

When oxygen is present in cells, polyphenol oxidase (PPO) enzymes in the chloroplasts rapidly oxidize phenolic compounds naturally present in the apple tissues to o-quinones, colorless precursors ...

And does it have to be brown bread? • When you slice a potato, an enzyme called polyphenol oxidase is released and catalyses a chemical reaction between polyphenols in the potato and oxygen from ...